The relevance of skill prick tests for Pityrosporum ovale in patients with head and neck dermatitis

Background: Patients with atopic dermatitis often develop immunoglobulin E antibodies against the yeast Pityrosporum ovale. This organism may produce positive skin prick reactions in a higher rate in patients with atopic dermatitis of the head, scalp, and neck region. Methods: We investigated whether positive prick tests to P. ovale were associated with a specific localization in the head and neck region. A total of 589 consecutive patients were prick tested with a P. ovale extract from ALK Abello. Results: Thirty-seven patients (6.3%) showed a positive reaction to the P. ovale extract. We could not find significant differences in the localizations of the dermatitis and the pattern of reaction to the tested intracutaneous allergens between the 37 patients positive to P. ovale and the control group of 55 subjects with negative reactions. In a subgroup, we found an elevated level of P. ovale-specific IgE in 100.0% of the patients with head and neck dermatitis, compared with 13.6% in the atopic dermatitis patients with lesions in any other localization. Conclusions: Our results clearly show that P. ovale-specific IgE is strongly related to the head and neck localization of atopic dermatitis, but RAST seems more sensitive than a prick test with the extract we used.